Testing for Antibodies to Human Immunodeficiency Virus Type 2
in the United States

This report was prepared by the following:

Thomas R. O'Brien, M.D., M.P.H. *

J. Richard George, Ph.D. *

Jay S. Epstein, M.D. **
Scott D. Holmberg, M.D., M.P.H. *

Gerald Schochetman, Ph.D. *

Centers for Disease Control

** Food and Drug Administration

Summary

The Food and Drug Administration (FDA) has recommended that
all
donated blood be screened for antibodies to human immunodeficiency
virus
type 2 (HIV-2) beginning no later than June 1, 1992. This article
provides
CDC recommendations for the diagnosis of HIV-1 and HIV-2 infections
in
persons being tested in settings other than blood centers and
CDC/FDA
guidelines for serologic testing with combination HIV-1/HIV-2
screening
enzyme immunoassays (EIAs).

Epidemiologic data indicate that the prevalence of HIV-2
infections in
persons in the United States is extremely low. Therefore, CDC does
not
recommend routine testing for HIV-2 in settings other than blood
centers.
However, when HIV testing is indicated, tests for antibodies to
both HIV-1
and HIV-2 should be obtained if epidemiologic risk factors for
HIV-2
infection are present, if clinical evidence exists for HIV disease
in the
absence of a positive test for antibodies to HIV-1, or if HIV-1
Western
blot results exhibit the unusual indeterminate pattern of gag plus
pol
bands in the absence of env bands.

The following procedures are recommended if testing for both
HIV-1 and
HIV-2 is performed by means of a combination HIV-1/HIV-2 EIA. A
repeatedly
reactive specimen by HIV-1/HIV-2 EIA should be tested by HIV-1
Western blot
(or another licensed HIV-2 supplemental test). A positive result by
HIV-1
Western blot confirms the presence of antibodies to HIV, and
testing for
HIV-2 is recommended only if HIV-2 risk factors are present. If the
HIV-1
Western blot result is negative or indeterminate, an HIV-2 EIA
should be
performed. If the HIV-2 EIA is positive, an HIV-2 supplemental test
should
be performed.

INTRODUCTION

Efforts to prevent transmission of human immunodeficiency
virus type 1
(HIV-1), particularly through the blood supply, led to the rapid
development in 1985 of diagnostic tests for HIV-1 antibodies. In
1986, a
second virus causing the acquired immunodeficiency syndrome (AIDS),
human
immunodeficiency virus type 2 (HIV-2), was discovered and found to
be
relatively common in parts of West Africa (1-3). Because HIV-2
infections
are not always detected by HIV-1 antibody tests (4), antibody tests
for
HIV-2 have been developed. On April 25, 1990, the Food and Drug
Administration (FDA) licensed an enzyme immunoassay (EIA) test kit
for
detection of antibodies to HIV-2 in human serum or plasma. The
test,
Genetic Systems HIV-2 EIA, manufactured and distributed by Genetic
Systems
Corp., Redmond, WA, is based on a disrupted whole-virus antigen
obtained by
purification of HIV-2 grown in cell culture. Licensure of the HIV-2
EIA
raised the possibility of routine donor screening for HIV-2.
However, after
public discussion at the FDA Blood Products Advisory Committee
meeting in
March 1990, FDA decided not to recommend routine anti-HIV-2
screening of
blood donated for transfusion. This decision was based on the
collective
evidence that HIV-2 infection in the United States was extremely
rare (5).
There was also reluctance to increase the complexity of testing
performed
by blood centers by introducing an additional test, of limited
usefulness,
to the battery of tests already being performed. However, voluntary
screening for HIV-2 antibodies by blood banks was considered to be
an
acceptable practice.

On September 25, 1991, FDA licensed the Genetic Systems
HIV-1/HIV-2
EIA and on February 14, 1992, licensed the HIVAB HIV-1/HIV-2 (rDNA)
EIA
(Abbott Laboratories, North Chicago, IL). These tests permit
simultaneous
testing for both HIV-1 and HIV-2 without increasing the number of
screening
tests performed by blood banks. In accordance with FDA
recommendations
effective June 1, 1992, blood centers have begun testing all
donated whole
blood, blood components, and source plasma for antibodies to HIV-2
(FDA:
Revised recommendations for the prevention of human
immunodeficiency virus
{HIV} transmission by blood and blood products {memorandum}.
Bethesda, MD:
Center for Biologics Evaluation and Research, FDA, April 23, 1992).
Blood
centers can accomplish this either by the use of a single
combination test
for HIV-1/HIV-2 or by the use of two independent tests, one for
HIV-1 and
one for HIV-2. Screening donated blood and plasma for HIV-2
infection
raises issues concerning appropriate strategies for testing for
both
viruses, HIV-2 testing in other settings, and notification of HIV-1
and
HIV-2 test results. This article provides CDC recommendations for
the
diagnosis of HIV-1 and HIV-2 infections in persons being tested in
settings
other than blood centers and CDC/FDA guidelines for serologic
testing with
combination HIV-1/HIV-2 screening EIAs.

EPIDEMIOLOGIC STUDIES

Although HIV-2 appears to have spread in West Africa primarily
via
heterosexual transmission (3), HIV-2 infection has been reported in
Europe
in homosexual men (6), injecting drug users (IDUs) (7), transfusion
recipients (8,9), and men with hemophilia (10). HIV-2 is endemic in
parts
of West Africa (3, 11, 12) and has also been reported in other
parts of
Africa (3) Table_1. Apparently as a result of links with former
colonies in West Africa, Portugal and France have reported the
highest
number of cases of HIV-2 infection in Europe (13). As of late 1989,
12.6%
of AIDS cases in Portugal were caused by HIV-2 (14). Although most
of these
cases were in persons originally from Africa, HIV-2 is also present
among
persons in Portugal with no known contacts with Africa. HIV-2
infection has
also been reported in India (15).

In the Western hemisphere, rare cases of HIV-2 infection have
been
reported from Brazil(16, 17), Canada (18), and the United States
(5).
Within the United States, CDC and others conduct surveillance for
HIV-2,
including serologic surveillance of blood donors and populations at
increased risk of HIV-1 infection.

Since 1987, 32 persons with HIV-2 infection have been reported
in the
United States. Fifteen of these 32 were identified by serologic
surveillance, and 17 were identified by case reports. Twenty-eight
were
residing in the northeastern United States (5), a frequent
destination for
West African immigrants and the area that has been most intensely
surveyed
using HIV-2-specific tests. No cases of HIV-2 infection have been
reported
among persons known to be IDUs or men reporting homosexual contact
(5).

More than 2,700 serum specimens that were reactive by HIV-1
EIA and
indeterminate by HIV-1 Western blot have been tested for HIV-2 by
either
the New York City Health Department or the Maryland Department of
Health
and Mental Hygiene (5, 19). HIV-2 infection was detected in
specimens from
11 persons. The Massachusetts Department of Public Health (5)
identified
two HIV-2-positive specimens among blood samples from 14,779
childbearing
women. Positive HIV-2 specimens were detected among sera from two
of 19,504
clients of sexually transmitted disease clinics, but in none of the
specimens from 6,547 IDUs at drug-treatment centers (20). In other
studies
of populations at increased risk for HIV-1 infection, no cases of
HIV-2
infection have been reported (5). Of 15 U.S. residents found to be
positive
for HIV-2 infection through serologic surveillance, demographic
information
was available for seven; six were West Africans and one was the
U.S.-born
wife of an HIV-2 infected West African (5).

Most of the 17 persons identified by case reports were West
Africans
residing in the United States, but one was a U.S. resident of
European
origin and two were native-born U.S. citizens (5). All three
non-West
Africans had traveled to West Africa. One native-born U.S. citizen
was
diagnosed as HIV-2 infected after volunteering to donate blood in
1986.
However, serologic surveillance of more than 26,000,000 blood
donations
collected between 1987 and 1991 has not revealed another instance
of an
HIV-2 infected U.S. blood donor (21-25).

DIAGNOSIS OF HIV-2 INFECTION

Although considerable serologic cross-reaction occurs between
HIV-1
and HIV-2, HIV-2 infection may not be diagnosed when screening is
done
exclusively with HIV-1 tests. From 60% to 91% of HIV-2-infected
persons
will test repeatedly reactive by HIV-1 whole-virus lysate EIA (4).
According to data provided to FDA by the test manufacturers, HIV-2
antibodies are detected with >99% sensitivity by FDA-licensed
HIV-1/HIV-2
EIAs and the FDA-licensed HIV-2 EIA. However, analogous to the
diagnosis of
HIV-1 infection, diagnosis of HIV-2 infection requires more
specific
supplemental tests, such as an HIV-2 Western blot. Although no
licensed
supplemental tests exist for HIV-2 infection, research tests are
available.

Several European and U.S. biotechnology companies manufacture
HIV-2
Western blot tests. Studies of these tests have been performed by
manufacturers of HIV test kits, by state and local public health
laboratories, and by CDC (26,27). The diversity of protein bands,
especially glycoprotein bands, is greater on the HIV-2 Western blot
tests
than on HIV-1 Western blot tests (28). This variation occurs
because the
various HIV-2 Western blot tests use different strains of HIV-2 and
because
of the different methods by which HIV-2 antigens are prepared
before
separation by electrophoresis (28). No one test appears to have a
distinct
advantage. Therefore, although public health laboratories would
benefit
from a standard HIV-2 Western blot test format to which a single
set of
interpretive criteria could be applied, a single standard currently
cannot
be applied to all tests. CDC recommends that each test be
interpreted by
the criteria suggested by the kit manufacturer.

Other investigational tests for antibodies to HIV-2, such as
immunofluorescence (29), EIAs based on HIV-1 and HIV-2 synthetic
peptides
(30), and radioimmune precipitation (31), can be useful in
distinguishing a
true positive HIV-2 EIA screening test result. Gene amplification
by
polymerase chain reaction (17) and viral culture (32) can also be
used to
determine the virus type.

RECOMMENDATIONS FOR HIV-2 TESTING IN THE UNITED STATES

Indications for Testing for HIV-2 Infection

Because epidemiologic data indicate that the prevalence of
HIV-2 in
the United States is extremely low, CDC does not recommend routine
testing
for HIV-2 at U.S. HIV counseling and test sites or in settings
other than
blood centers. However, when HIV testing is to be performed, tests
for
antibodies to both HIV-1 and HIV-2 should be obtained if
demographic or
behavioral information suggests that HIV-2 infection might be
present.
Persons at risk for HIV-2 infection include:

Sex partners of a person from a country where HIV-2 is
endemic
(this category includes persons originally from such
countries).

Sex partners of a person known to be infected with HIV-2.

Persons who received a transfusion of blood or a
nonsterile
injection in a country where HIV-2 is endemic.

Persons who shared needles with a person from a country
where
HIV-2 is endemic or with a person known to be infected
with
HIV-2.

Children of women who have risk factors for HIV-2
infection or
who are known to be infected with HIV-2.
Additionally, testing for HIV-2 is indicated when there is
clinical

evidence for or suspicion of HIV disease (such as an
AIDS-associated
opportunistic infection)in the absence of a positive test for
antibodies to
HIV-1 and in cases in which the HIV-1 Western blot exhibits the
unusual
indeterminate pattern of gag (p55, p24, or p17) plus pol (p66, p51,
or p32)
bands in the absence of env (gp160, gp120, Or gp41) bands.

Other Considerations

The potential risk of HIV-2 infection in some populations
(such as
those described above) may justify routine HIV-2 testing for all
persons
for whom HIV-1 testing is warranted. The decision to implement
routine
HIV-2 testing requires consideration of the number of
HIV-2-infected
persons who would remain undiagnosed without routine HIV-2 testing
compared
with the problems and costs associated with its implementation.

Because implementation of routine HIV-2 testing would increase
the
number of tests performed on some specimens and because
confirmatory
testing for HIV-2 would be limited to laboratories that perform
nonlicensed
HIV-2 supplemental tests, the maximum "turnaround" time required to
complete HIV testing would increase for some specimens. At HIV
counseling
and test sites, clients might require an additional appointment
after the
routine post-test counseling session to receive HIV-2 test results
and
HIV-2 post-test counseling. Another factor to consider when routine
HIV-2
testing is being contemplated is the predictive value of HIV-2
antibody
screening tests in most U.S. populations. Given the extremely low
prevalence of HIV-2 in the United States, very few persons who test
positive by HIV-2 antibody screening tests will actually be HIV-2
infected
In addition, HIV-2 testing may identify persons with indeterminate
HIV-2
test results that must be explained to the patient and appropriate
follow-up initiated. Finally, implementation of routine HIV-2
testing would
increase HIV testing costs, as HIV-1/HIV-2 combination EIAs are
more
expensive than HIV-1 EIAs, and testing with HIV-2 EIAs and
supplemental
tests would be required for some specimens.

Laboratories that use a licensed combination HIV-1/HIV-2
screening
test should follow the testing algorithm recommended by CDC and FDA
Figure_1. If a combination test for HIV-1/HIV-2 is performed
and is
repeatedly reactive, additional, more specific testing is necessary
to
confirm the presence of antibodies either to HIV-1 or HIV-2 as
follows:

A repeatedly reactive specimen determined by a
combination
HIV-1/HIV-2 EIA should be tested for antibodies to HIV-1
by a
licensed Western blot or other licensed HIV-1
supplemental test.
A positive HIV-1 Western blot confirms the presence of
antibodies
to HIV. Although this result does not always distinguish
between
antibodies to HIV-1 and HIV-2, further testing is not
required
for routine purposes. If the suspicion of HIV-2 infection
(based
on epidemiologic risk factors {see "Recommendations"
section}) is
high, additional testing for HIV-2 is indicated.

If the HIV-1 Western blot result is negative or
indeterminate, an
EIA for HIV-2 only (HIV-2 EIA) should be performed. If
the HIV-1
Western blot is negative and HIV-2 EIA is not repeatedly
reactive, the specimen should be considered negative for
HIV
antibodies. If the HIV-1 Western blot is indeterminate
and the
HIV-2 EIA is not repeatedly reactive, the specimen should
be
considered indeterminate and the person should be advised
to have
follow-up testing 6 months later to exclude the
possibility of
early infection with HIV-1, especially if risk factors
are
present. Persons should be counseled to follow
risk-reduction
guidelines during the intervening 6 months (33). If the
HIV-1
immunofluorescence assay (IFA) is used as the
supplemental test,
positive and negative IFA results should be interpreted
in the
same manner as similar results from Western blot tests.
However,
with an indeterminate IFA (both infected and uninfected
cells
fluoresce), neither positive nor negative interpretation
of the
test is possible. Therefore, the specimen should be
tested by
HIV-1 Western blot. Further testing and counseling are
determined
by the results of the Western blot.

If the HIV-2 EIA is repeatedly reactive, an HIV-2
supplemental
test should be performed. Until an FDA-licensed
supplemental test
for HIV-2 becomes available, specimens requiring
supplemental
testing for HIV-2 should be sent to the appropriate state
public
health laboratory. Only those sera that are repeatedly
reactive
by the combination HIV-1/HIV-2 test, negative or
indeterminate by
the HIV-1 Western blot, and positive by the licensed
HIV-2 EIA
should be sent for supplemental HIV-2 testing. An
exception to
this rule would be a person with a positive result by
HIV-1
Western blot, but with demographic risk factors for HIV-2
infection.

Retesting with a second specimen should be considered for
persons
who have positive results by HIV-1 or HIV-2 Western blot
at first
testing.

MEDICAL COUNSELING

Infection with either HIV-1 or HIV-2 can cause
immunosuppression and
the development of AIDS (34,35). Although the period between
infection and
disease may be longer for persons with HIV-2 than for those with
HIV-1
(36,37), the modes of transmission and, therefore, preventive
counseling
are the same for persons with either virus. Furthermore, because
data are
limited regarding the effectiveness of antiviral therapy for HIV-2
infection, persons with a confirmed antibody test for HIV-2 should
be
managed similarly to persons with a confirmed antibody test for
HIV-1.
Additional testing to define the virus type is of epidemiologic
importance
and should be considered for persons with epidemiologic risk
factors for
infection with HIV-2.

Based on the epidemiology and prevalence of HIV-2 in the
United
States, CDC/FDA makes the following recommendations for
notification of
persons with repeatedly reactive combination screening tests for
HIV-1/HIV-2.

If the HIV-1 Western blot is positive, the person should
be
considered to be HIV infected and counseled and managed
as if
infected with HIV-1. In infants, detection of antibodies
soon
after birth may indicate either infection or the presence
of
maternal HIV antibodies. Seropositive infants require
additional
follow-up to determine their HIV status.

If the HIV-1 Western blot is negative and HIV-2 EIA is
not
repeatedly reactive, the person should be informed that
the test
results for HIV infection are negative.

If an HIV-2 EIA is repeatedly reactive for a person with
a
negative or indeterminate HIV-1 Western blot, post-test
counseling will depend on the results of the HIV-2
supplemental
test. A person should not be diagnosed or counseled about
HIV-2
infection on the basis of a repeatedly reactive HIV-2 EIA
alone.
in the absence of known epidemiologic risk factors for
HIV-2
infection, the vast majority of specimens from persons in
the
United States with a repeatedly reactive HIV-2 EIA and
negative
or indeterminate HIV-1 Western blot will represent
false-positive
results.

If the HIV-2 supplemental test is negative, a person
whose
specimen was negative by HIV-1 Western blot, in the
absence
of recognized epidemiologic risk factors, should be
considered to be uninfected with HIV and counseled
accordingly. A person whose specimen was
indeterminate by
HIV-1 Western blot should be followed as previously
recommended (38).

If the HIV-2 supplemental test is positive, the
person
should be considered to be HIV infected and
counseled and
managed accordingly. The case should be reported to
the
state department of public health as presumptive
HIV-2
infection.

If the HIV-2 supplemental test is indeterminate, the
person
should have follow-up testing 6 months later to
exclude the
possibility of early infection with HIV-1 or HIV-2.

If an HIV-2 EIA is not repeatedly reactive for a person
with an
indeterminate HIV-1 Western blot, the person should be
followed
as previously recommended (38).

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